Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 95
Filtrar
1.
Phys Med Biol ; 2021 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-33721860

RESUMO

Myocardial perfusion imaging (MPI) with PET plays a vital role in the management of coronary artery disease. High sensitivity systems can contribute to maximizing the potential value of PET MPI; therefore, we have proposed two novel detector arrangements, an elliptical geometry and a D-shape geometry, that are more sensitive and more compact than a conventional large-bore cylindrical geometry. Here we investigate two items: the benefits of the proposed geometries for cardiac imaging; and the effects of scatter components on cardiac PET image quality. Using the Geant4 toolkit, we modeled four time-of-flight (TOF) PET systems: an 80-cm-diameter cylinder, a 40-cm-diameter cylinder, a compact ellipse, and a compact D-shape. Spatial resolution and sensitivity were measured using point sources. Noise equivalent count rate (NECR) and image quality were examined using an anthropomorphic digital chest phantom. The proposed geometries showed higher sensitivity and better count rate characteristics with a fewer number of detectors than the conventional large-bore cylindrical geometry. In addition, we found that the increased intensity of the scatter components was a big factor affecting the contrast in defect regions for such a compact geometry. It is important to address the issue of the increased intensity of the scatter components to develop a high-performance compact cardiac TOF PET system.

2.
Phys Med Biol ; 66(6): 065013, 2021 Mar 08.
Artigo em Inglês | MEDLINE | ID: mdl-33607635

RESUMO

The crosshair light-sharing (CLS) PET detector is our original depth-of-interaction (DOI) detector, which is based on a single-ended readout scheme with quadrisected crystals comparable in size to a photo-sensor. In this work, we developed 32 CLS PET detectors, each of which consisted of a multi-pixel photon counter (MPPC) array and gadolinium fine aluminum garnet (GFAG) crystals, and we developed a benchtop prototype of a small animal size PET. Each GFAG crystal was 1.45 × 1.45 × 15 mm3. The MPPC had a surface area of 3.0 × 3.0 mm2. The benchtop prototype had two detector rings of 16 detector blocks. The ring diameter and axial field-of-view were 14.2 cm and 4.9 cm, respectively. The data acquisition system used was the PETsys silicon photomultiplier readout system. The continuous DOI information was binned into three DOI layers by applying a look-up-table to a 2D position histogram. Also, energy and timing information was corrected using DOI information. After the calibration procedure, the energy resolution and the coincidence time resolution were 14.6% and 531 ps, respectively. Imaging test results of a small rod phantom obtained by an iterative reconstruction method showed clear separation of 1.6 mm rods with the help of DOI information.

3.
Phys Med Biol ; 65(23): 235052, 2020 Dec 05.
Artigo em Inglês | MEDLINE | ID: mdl-33283764

RESUMO

This work presents an iterative method for the estimation of the absolute dose distribution in patients undergoing carbon ion therapy, via analysis of the distribution of positron annihilations resulting from the decay of positron-emitting fragments created in the target volume. The proposed method relies on the decomposition of the total positron-annihilation distributions into profiles of the three principal positron-emitting fragment species - 11C, 10C and 15O. A library of basis functions is constructed by simulating a range of monoenergetic 12C ion irradiations of a homogeneous polymethyl methacrylate phantom and measuring the resulting one-dimensional positron-emitting fragment profiles and dose distributions. To estimate the dose delivered during an arbitrary polyenergetic irradiation, a linear combination of factors from the fragment profile library is iteratively fitted to the decomposed positron annihilation profile acquired during the irradiation, and the resulting weights combined with the corresponding monoenergetic dose profiles to estimate the total dose distribution. A total variation regularisation term is incorporated into the fitting process to suppress high-frequency noise. The method was evaluated with 14 different polyenergetic 12C dose profiles in a polymethyl methacrylate target: one which produces a flat biological dose, 10 with randomised energy weighting factors, and three with distinct dose maxima or minima within the spread-out Bragg peak region. The proposed method is able to calculate the dose profile with mean relative errors of 0.8%, 1.0% and 1.6% from the 11C, 10C, 15O fragment profiles, respectively, and estimate the position of the distal edge of the SOBP to within an average of 0.7 mm, 1.9 mm and 1.2 mm of its true location.

4.
Phys Med Biol ; 65(23): 235051, 2020 12 18.
Artigo em Inglês | MEDLINE | ID: mdl-33336650

RESUMO

The purpose of this work is to develop a validated Geant4 simulation model of a whole-body prototype PET scanner constructed from the four-layer depth-of-interaction detectors developed at the National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Japan. The simulation model emulates the behaviour of the unique depth of interaction sensing capability of the scanner without needing to directly simulate optical photon transport in the scintillator and photodetector modules. The model was validated by evaluating and comparing performance metrics from the NEMA NU 2-2012 protocol on both the simulated and physical scanner, including spatial resolution, sensitivity, scatter fraction, noise equivalent count rates and image quality. The results show that the average sensitivities of the scanner in the field-of-view were 5.9 cps kBq-1 and 6.0 cps kBq-1 for experiment and simulation, respectively. The average spatial resolutions measured for point sources placed at several radial offsets were 5.2± 0.7 mm and 5.0± 0.8 mm FWHM for experiment and simulation, respectively. The peak NECR was 22.9 kcps at 7.4 kBq ml-1 for the experiment, while the NECR obtained via simulation was 23.3 kcps at the same activity. The scatter fractions were 44% and 41.3% for the experiment and simulation, respectively. Contrast recovery estimates performed in different regions of a simulated image quality phantom matched the experimental results with an average error of -8.7% and +3.4% for hot and cold lesions, respectively. The results demonstrate that the developed Geant4 model reliably reproduces the key NEMA NU 2-2012 performance metrics evaluated on the prototype PET scanner. A simplified version of the model is included as an advanced example in Geant4 version 10.5.


Assuntos
Método de Monte Carlo , Tomografia por Emissão de Pósitrons/instrumentação , Imagem Corporal Total/instrumentação , Desenho de Equipamento , Imagens de Fantasmas , Fótons
5.
Phys Med Biol ; 2020 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-32937613

RESUMO

Compton imaging or Compton camera imaging has been studied well, but its advantages in nuclear medicine and molecular imaging have not been demonstrated yet. Therefore, the aim of this work was to compare Compton imaging with positron emission tomography (PET) by using the same imaging platform of whole gamma imaging (WGI). WGI is a concept that combines PET with Compton imaging by inserting a scatterer ring into a PET ring. This concept utilizes diverse types of gamma rays for 3D tomographic imaging. In this paper, we remodeled our previous WGI prototype for small animal imaging, and we developed an image reconstruction method based on a list-mode ordered subset expectation maximization algorithm incorporating detector response function (DRF) modeling, random correction and normalization (sensitivity correction) for either PET and Compton imaging. To the best of our knowledge, this is the world's first realization of a full-ring Compton imaging system. We selected89Zr as an imaging target because a89Zr nuclide emits a 909 keV single-gamma ray as well as a positron, and we can directly compare Compton imaging of 909 keV photons with PET, a well-established modality. We measured a cylindrical phantom and a small rod phantom filled with89Zr solutions of 10.3 MBq and 10.2 MBq activity, respectively, for 1 hour each. The uniform radioactivity distribution of the cylindrical phantom was reconstructed with normalization in both PET and Compton imaging. Coefficients of variation for region-of-interest values were 4.2% for Compton imaging and 3.3% for PET; the difference might be explained by the difference in the detected count number. The small rod phantom experiment showed that the WGI Compton imaging had spatial resolution better than 3.0 mm at the peripheral region although the center region had lower resolution. PET resolved 2.2-mm rods clearly at any location. We measured a mouse for 1 hour, 1 day after injection of 9.8 MBq89Zr oxalate. The89Zr assimilated in the mouse bony structures was clearly depicted, and Compton imaging results agreed well with PET images, especially for the region inside the scatterer ring. In conclusion, we demonstrated the performance of WGI using the developed Compton image reconstruction method. We realized Compton imaging with a quality approaching that of PET, which is supporting a future expectation that Compton imaging outperforms PET.

6.
Hinyokika Kiyo ; 66(7): 235-238, 2020 Jul.
Artigo em Japonês | MEDLINE | ID: mdl-32723979

RESUMO

A female septuagenarian had poorly controlled diabetes mellitus for more than 20 years. She had persistent pyuria, but did not seek further examination. In 2019, she was transported to our hospital by ambulance for sudden abdominal pain. Physical examination showed a sign of panperitonitis with sepsis. Computed tomography showed ascites and intraperitoneal free air. In addition, there was also a defect in the bladder wall, suggesting bladder rupture. Blood tests showed a marked increase in serum creatinine in addition to increased inflammatory reactants. Because perforation of gastrointestinal tract could not be excluded, an emergency laparotomy was performed. An intraperitoneal perforation of the posterior wall of the bladder was revealed, though there was no intestinal damage. The bladder wall was repaired and cystostomy was performed followed by irrigation and drainage of the abdominal cavity. After the operation, her abdominal symptom resolved and her general status improved. We speculated that voiding disturbance due to neurogenic bladder associated with diabetes mellitus and chronic infection caused the spontaneous bladder rupture. Most cases of spontaneous bladder rupture are associated with a history of pelvic surgery or irradiation, which suggests that this case is extremely rare. In patients with repeated urinary tract infection and underlying disease affecting bladder function, evaluation and appropriate management of bladder dysfunction should be performed ; otherwise, spontaneous bladder rupture may occur.


Assuntos
Doenças da Bexiga Urinária , Bexiga Urinaria Neurogênica , Cistostomia , Feminino , Humanos , Ruptura Espontânea
7.
Dent Mater J ; 39(6): 1039-1043, 2020 Dec 03.
Artigo em Inglês | MEDLINE | ID: mdl-32624550

RESUMO

We investigated the adsorption of lipoteichoic acid (LTA) on titanium surfaces by using the quartz crystal microbalance (QCM) method, and confirmed the influence of mucin (MUC) pre-adsorption on LTA adsorption. Two injection methods were evaluated. Namely, Method A: single-step injection of LTA solution to the Ti sensor, and Method B: MUC solution was injected to the Ti sensor followed by LTA injection on the MUC pre-adsorbed surface. QCM measurement revealed that the adsorbed amount of LTA by Method A was low and constant regardless of the increase in LTA concentration. In contrast, the adsorption amount of LTA in Method B increased according with increasing concentration of LTA and was significantly higher than that of Method A. The hydrophobic surface after MUC pre-adsorption was presumed to contribute to the enhancement of LTA adsorption. Our results revealed that MUC pre-adsorption to Ti is necessary for LTA adsorption in living tissue.

8.
Phys Med Biol ; 65(14): 145008, 2020 07 20.
Artigo em Inglês | MEDLINE | ID: mdl-32325448

RESUMO

Brain PET, which has led research in molecular imaging and diagnosis of brain cancer, epilepsy and neurodegenerative disorders, is being spotlighted again to promote earlier diagnosis of dementia with the advent of amyloid and tau tracers. To meet this demand, in this paper, we developed a brain-dedicated PET imaging device with a hemispherical detector arrangement, which provides comparable sensitivity with fewer detectors than conventional cylindrical geometries. The introduction of the time-of-flight (TOF) measurement capability was a key point for the development to get a gain in the image signal-to-noise ratio. Currently, whole-body PET scanners with around 200-400 ps coincidence resolving time (CRT) are commercially available. In order to obtain the same TOF gain which can be obtained with 400 ps CRT for a 30 cm diameter object, 267 ps CRT will be required for a 20 cm diameter object such as the human head. In this work, therefore, we aimed at developing a TOF brain-dedicated PET prototype with the hemisphere detector arrangement and the CRT faster than 267 ps. The detector was composed of a 12 × 12 lutetium fine silicate (LFS) array coupled with a 12 × 12 multi-pixel photon counter (MPPC) array. Each LFS crystal with a size of 4.14 × 4.14 × 10 mm3 was individually coupled to a separate MPPC. Singles list-mode data from each detector were stored, and coincidences were identified using a coincidence-detection software algorithm. The CRT of 245 ps was finally achieved as the system average after a fine timing correction. For image reconstruction, we implemented the list-mode TOF-OSEM. For a small rod phantom, rods of 3 mm diameter were clearly separated. Also, images of the 3D Hoffman brain phantom, which demonstrated clear contrast between gray and white matter, supported the effect of TOF information.


Assuntos
Encéfalo/diagnóstico por imagem , Tomografia por Emissão de Pósitrons/instrumentação , Algoritmos , Humanos , Processamento de Imagem Assistida por Computador , Lutécio/química , Imagens de Fantasmas , Fótons
9.
Phys Med Biol ; 65(12): 125013, 2020 06 18.
Artigo em Inglês | MEDLINE | ID: mdl-32348968

RESUMO

We proposed a concept of whole gamma imaging (WGI) that utilizes all detectable gamma rays for imaging. An additional detector ring, which is used as the scatterer, is inserted in the field-of-view of a PET ring so that single gamma rays can be detected by the Compton imaging method. In particular, for the non-pure positron emitters which emit an additional gamma ray almost at the same time, triple gamma imaging will be enabled; localization on each line-of-response (LOR) is possible by using the Compton cone of the additional gamma ray. We developed a prototype to show a proof of the WGI concept. The diameters of scatterer ring and PET ring were set as 20 cm and 66 cm, respectively. For Compton imaging of the 662-keV gamma ray from a 137Cs point source, spatial resolution obtained by the list-mode OSEM algorithm was 4.4 mm FWHM at the 8 cm off-center position and 13.1 mm FWHM at the center position. For PET imaging of a 22Na point source, spatial resolution was about 2 mm FWHM at all positions. For the triple gamma imaging, 5.7 mm FWHM (center) and 4.8 mm FWHM (8 cm off-center) were obtained for the 22Na point source just by plotting the intersecting points between each LOR and each Compton cone of the 1275-keV gamma ray. No image reconstruction was applied. Scandium-44 was produced as a practical candidate of the non-pure positron emitters, and 6.6 mm FWHM (center) and 5.8 mm FWHM (8 cm off-center) were obtained in the same manner. This direct imaging approach which neither requires time-consuming event integration nor iterative image reconstruction may allow in vivo real-time tracking of a tiny amount of activity. Our initial results showed the feasibility of the WGI concept, which is a novel combination of PET and Compton imaging.


Assuntos
Raios gama , Tomografia por Emissão de Pósitrons/métodos , Algoritmos , Radioisótopos de Césio , Elétrons , Processamento de Imagem Assistida por Computador , Imagens de Fantasmas , Fótons , Radioisótopos , Escândio
10.
Sci Rep ; 10(1): 4143, 2020 03 10.
Artigo em Inglês | MEDLINE | ID: mdl-32157106

RESUMO

Pancreatic cancer (PC) has a poor prognosis owing to difficulties in the diagnosis of resectable PC at early stages. Several clinical studies have indicated that the detection and surgery of small resectable PC (<1 cm) can significantly improve survival; however, imaging diagnosis and accurate resection of small PC remain challenging. Here, we report the feasibility of "immuno-OpenPET" as a novel approach enabling not only early diagnosis but also image-guided surgery, using a small (<1 cm) resectable PC orthotopic xenograft mouse model. For immuno-OpenPET, we utilized our original OpenPET system, which enables high-resolution positron emission tomography (PET) imaging with depth-of-interaction detectors, as well as real-time image-guided surgery, by arranging the detectors to create an open space for surgery and accelerating the image reconstruction process by graphics processing units. For immuno-OpenPET, 64Cu-labeled anti-epidermal growth factor receptor antibody cetuximab was intraperitoneally administered into mice. It clearly identified PC tumors ≥3 mm. In contrast, neither OpenPET with intravenous-administered 64Cu-cetuximab nor intraperitoneal/intravenous-administered 18F-FDG (a traditional PET probe) could detect PC in this model. Immuno-OpenPET-guided surgery accurately resected small PC in mice and achieved significantly prolonged survival. This technology could provide a novel diagnostic and therapeutic strategy for small resectable PC to improve patient survival.


Assuntos
Cetuximab/imunologia , Radioisótopos de Cobre/metabolismo , Detecção Precoce de Câncer/métodos , Neoplasias Pancreáticas/patologia , Tomografia por Emissão de Pósitrons/métodos , Cirurgia Assistida por Computador/métodos , Animais , Antineoplásicos Imunológicos/imunologia , Apoptose , Proliferação de Células , Feminino , Humanos , Processamento de Imagem Assistida por Computador , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Nus , Neoplasias Pancreáticas/diagnóstico por imagem , Neoplasias Pancreáticas/metabolismo , Neoplasias Pancreáticas/cirurgia , Compostos Radiofarmacêuticos/metabolismo , Células Tumorais Cultivadas , Ensaios Antitumorais Modelo de Xenoenxerto
11.
Phys Med Biol ; 65(12): 125006, 2020 06 15.
Artigo em Inglês | MEDLINE | ID: mdl-32176873

RESUMO

In heavy-ion therapy, the stopping position of primary ions in tumours needs to be monitored for effective treatment and to prevent overdose exposure to normal tissues. Positron-emitting ion beams, such as 11C and 15O, have been suggested for range verification in heavy-ion therapy using in-beam positron emission tomography (PET) imaging, which offers the capability of visualizing the ion stopping position with a high signal-to-noise ratio. We have previously demonstrated the feasibility of in-beam PET imaging for the range verification of 11C and 15O ion beams and observed a slight shift between the beam stopping position and the dose peak position in simulations, depending on the initial beam energy spread. In this study, we focused on the experimental confirmation of the shift between the Bragg peak position and the position of the maximum detected positron-emitting fragments via a PET system for positron-emitting ion beams of 11C (210 MeV u-1) and 15O (312 MeV u-1) with momentum acceptances of 5% and 0.5%. For this purpose, we measured the depth doses and performed in-beam PET imaging using a polymethyl methacrylate (PMMA) phantom for both beams with different momentum acceptances. The shifts between the Bragg peak position and the PET peak position in an irradiated PMMA phantom for the 15O ion beams were 1.8 mm and 0.3 mm for momentum acceptances of 5% and 0.5%, respectively. The shifts between the positions of two peaks for the 11C ion beam were 2.1 mm and 0.1 mm for momentum acceptances of 5% and 0.5%, respectively. We observed larger shifts between the Bragg peak and the PET peak positions for a momentum acceptance of 5% for both beams, which is consistent with the simulation results reported in our previous study. The biological doses were also estimated from the calculated relative biological effectiveness (RBE) values using a modified microdosimetric kinetic model (mMKM) and Monte Carlo simulation. Beams with a momentum acceptance of 5% should be used with caution for therapeutic applications to avoid extra dose to normal tissues beyond the tumour when the dose distal fall-off is located beyond the treatment volume.


Assuntos
Radioisótopos de Carbono/uso terapêutico , Radioterapia com Íons Pesados/métodos , Radioisótopos de Oxigênio/uso terapêutico , Tomografia por Emissão de Pósitrons/métodos , Humanos , Método de Monte Carlo , Movimento (Física) , Imagens de Fantasmas , Eficiência Biológica Relativa
12.
Phys Med Biol ; 65(3): 035012, 2020 02 04.
Artigo em Inglês | MEDLINE | ID: mdl-31855854

RESUMO

Time-of-flight (TOF) is now a standard technology for positron emission tomography (PET), but its effective use for small diameter PET systems has not been studied well. In this paper, we simulated a brain-dedicated TOF-PET system with a hemispherical detector arrangement. We modeled a Hamamatsu TOF-PET module (C13500-4075LC-12) with 280 ps coincidence resolving time (CRT), in which a 12 × 12 array of multi pixel photon counters (MPPCs) is connected to a lutetium fine silicate (LFS) crystal array of 4.1 × 4.1 mm2 cross section each, based on one-to-one coupling. On the other hand, spatial resolution degradation due to the parallax error should be carefully addressed for the small diameter PET systems. The ideal PET detector would have both depth-of-interaction (DOI) and TOF capabilities, but typical DOI detectors that are based on light sharing tend to degrade TOF performance. Therefore, in this work, we investigated non-DOI detectors with an appropriate crystal length, which was a compromise between suppressed parallax error and decreased sensitivity. Using GEANT4, we compared two TOF detectors, a 20 mm long non-DOI and a 10 mm long non-DOI, with a non-TOF, 4-layer DOI detector with a total length of 20 mm (i.e. 5 × 4 mm). We simulated a contrast phantom and evaluated the relationship between the contrast recovery coefficient (CRC) and the noise level (the coefficient of variation, COV) for reconstructed images. The 10 mm long non-DOI, which reduces the parallax error at the cost of sensitivity loss, showed better imaging quality than the 20 mm long non-DOI. For example, the CRC value of a 10 mm hot sphere at COV = 20% was 72% for the 10 mm long non-DOI, which was 1.2 times higher than that of the 20 mm long non-DOI. The converged CRC values for the 10 mm long non-DOI were almost equivalent to those of the non-TOF 4-layer DOI, and the 10 mm long non-DOI converged faster than the non-TOF 4-layer DOI did. Based on the simulation results, we evaluated a one-pair prototype system of the TOF-PET detectors with 10 mm crystal length, which yielded the CRT of 250 ± 8 ps. In summary, we demonstrated support for feasibility of the brain-dedicated TOF-PET system with the hemispherical detector arrangement.


Assuntos
Encéfalo/diagnóstico por imagem , Imagens de Fantasmas , Fótons , Tomografia por Emissão de Pósitrons/instrumentação , Tomografia por Emissão de Pósitrons/métodos , Desenho de Equipamento , Humanos , Processamento de Imagem Assistida por Computador/métodos , Lutécio/química , Método de Monte Carlo , Projetos de Pesquisa , Silicatos/química
13.
Phys Med Biol ; 64(15): 155014, 2019 08 07.
Artigo em Inglês | MEDLINE | ID: mdl-31167173

RESUMO

The distribution of fragmentation products predicted by Monte Carlo simulations of heavy ion therapy depend on the hadronic physics model chosen in the simulation. This work aims to evaluate three alternative hadronic inelastic fragmentation physics options available in the Geant4 Monte Carlo radiation physics simulation framework to determine which model most accurately predicts the production of positron-emitting fragmentation products observable using in-beam PET imaging. Fragment distributions obtained with the BIC, QMD, and INCL + + physics models in Geant4 version 10.2.p03 are compared to experimental data obtained at the HIMAC heavy-ion treatment facility at NIRS in Chiba, Japan. For both simulations and experiments, monoenergetic beams are applied to three different block phantoms composed of gelatin, poly(methyl methacrylate) and polyethylene. The yields of the positron-emitting nuclei 11C, 10C and 15O obtained from simulations conducted with each model are compared to the experimental yields estimated by fitting a multi-exponential radioactive decay model to dynamic PET images using the normalised mean square error metric in the entrance, build up/Bragg peak and tail regions. Significant differences in positron-emitting fragment yield are observed among the three physics models with the best overall fit to experimental 12C and 16O beam measurements obtained with the BIC physics model.


Assuntos
Radioterapia com Íons Pesados/métodos , Planejamento da Radioterapia Assistida por Computador/métodos , Software/normas , Carbono/uso terapêutico , Método de Monte Carlo , Oxigênio/uso terapêutico , Imagens de Fantasmas , Planejamento da Radioterapia Assistida por Computador/normas
14.
World J Surg Oncol ; 17(1): 76, 2019 Apr 30.
Artigo em Inglês | MEDLINE | ID: mdl-31039791

RESUMO

BACKGROUND: Portal annular pancreas (PAP) is a rare congenital anatomical abnormality of the pancreas in which the portal vein is encircled by aberrant parenchyma, and special attention is needed for pancreatic resections. This is the first report of central pancreatectomy (CP) in a PAP for metastatic renal cell carcinoma (RCC). CASE PRESENTATION: A 76-year-old man who had a history of left nephrectomy for renal cancer not otherwise specified 36 years earlier and radical cystectomy for bladder cancer 4 years earlier was incidentally found to have a pancreatic tumor and a liver tumor. The pancreatic tumor was diagnosed as metastasis of clear cell RCC, and the liver tumor was diagnosed as moderately differentiated hepatocellular carcinoma (HCC) on preoperative histological evaluation. Preoperative computed tomography imaging showed a type 3A PAP, in which the main pancreatic duct (MPD) ran ventral to the portal vein (anteportal type), and the aberrant parenchyma was located cranial to the confluence of the portal vein and splenic vein (suprasplenic type). After adhesiotomy and partial liver resection, CP was performed. With intraoperative ultrasound guidance, the aberrant parenchyma of the PAP could be preserved, avoiding additional resection. Thus, two pancreatic transections were performed, creating a single-cut margin that contained the MPD in the distal pancreas. Oncologically safe margins were confirmed by intraoperative pathological diagnosis. The distal pancreas was reconstructed by pancreatojejunostomy in the routine procedures. The pathological diagnosis of the surgical specimens was identical to the preoperative diagnosis. A postoperative pancreatic fistula (POPF) developed from the proximal stump of the head of the pancreas, necessitating no specific treatment other than drainage. The patient showed no signs or symptoms of recurrent RCC or abnormal pancreatic function for 2 years after the operation, although a histologically proven new HCC lesion developed distant from the initial site 8 months after the operation. CONCLUSIONS: Precise preoperative evaluation of the tumor features and PAP allowed adequate surgical strategies to be planned. Intraoperative ultrasound was useful to minimize parenchymal resections of the PAP. CP is still a challenging procedure in terms of the development of POPF.


Assuntos
Carcinoma de Células Renais/cirurgia , Neoplasias Renais/cirurgia , Pâncreas/anormalidades , Pancreatectomia/métodos , Pancreatopatias/cirurgia , Veia Porta/cirurgia , Complicações Pós-Operatórias , Idoso , Carcinoma de Células Renais/secundário , Humanos , Neoplasias Renais/patologia , Masculino , Pâncreas/patologia , Pâncreas/cirurgia , Pancreatopatias/patologia , Veia Porta/patologia , Prognóstico
15.
Phys Med Biol ; 64(14): 145014, 2019 07 16.
Artigo em Inglês | MEDLINE | ID: mdl-31146265

RESUMO

In advanced ion therapy, the visualization of the range of incident ions in a patient's body is important for exploiting the advantages of this type of therapy. It is ideal to use radioactive ion beams for in-beam positron emission tomography (PET) imaging in particle therapy due to the high quality of PET images caused by the high signal-to-noise ratio. We have shown the feasibility of this idea through an in-beam PET study for 11C and 15O ion beams using the dedicated OpenPET system. In this work, we investigate the potential difference between the Bragg peak position and the position of the maximum detected positron-emitting fragments by a PET system for the radioactive beams of 11C and 15O. For this purpose, we measured the depth dose in a water phantom and performed PET scans of an irradiated PMMA phantom for the available beams of 11C and 15O at the Heavy Ion Medical Accelerator in Chiba (HIMAC). Then, we simulated the depth dose profiles in the water phantom and the yield of the positron-emitting fragments in a PMMA phantom for both available beams using the Monte Carlo code PHITS. The positions of the Bragg peak and maximum positron-emitting fragments from the measurements were well reproduced by simulation. The effect of beam energy broadening on the positional differences between two peaks was studied by simulating an irradiated PMMA phantom. The differences in position between the Bragg peak and the maximum positron-emitting fragments increased when the beam energy spread was broadened, although the differences were zero for the ideal mono-energetic beams. Greater differences were observed for 11C ion beams compared to 15O ion beams, although both beams had the same range in water, and the higher energy corresponded to a larger difference. For the known energy spread of the beams, the predicted differences between two peaks from the simulation were consistent with the measured data within submillimetre agreement.


Assuntos
Radioisótopos de Carbono/análise , Interpretação de Imagem Assistida por Computador/métodos , Radioisótopos de Oxigênio/análise , Imagens de Fantasmas , Tomografia por Emissão de Pósitrons/métodos , Simulação por Computador , Humanos , Método de Monte Carlo
16.
Phys Med Biol ; 64(12): 125003, 2019 06 10.
Artigo em Inglês | MEDLINE | ID: mdl-31096205

RESUMO

Some recently developed brain-dedicated positron emission tomography (PET) scanners measure subjects in a sitting position. Sitting enables PET scanning under more natural conditions for the subjects and also helps with making the scanners smaller. It is unclear, however, how much the degree of head motion when sitting differs from the supine posture commonly employed in clinical PET. In this report, we describe development of a markerless and contactless head motion tracking system and a study of healthy volunteers in several different postures to determine the optimum posture for brain PET. We used Kinect® (Microsoft) and developed software that can measure head motion with about 1 mm (translation) and less than 1° (rotation) accuracy. In the volunteer study, we measured the amount of head motion, with and without head fixation, in supine, normal sitting, and reclining postures. The results indicated that the normal sitting posture without head fixation had the largest head movement, and that the reclining and supine postures were similarly effective for minimizing head movement (average head movement of about 0.5 mm during 1 min). We also visualized the influence that head motion had on images for each pose by simulating the actual motions obtained from the volunteer study using a digital Hoffman phantom. Comparisons with the original image showed that the extent to which motion was reduced in the reclining and supine postures were quantitatively equivalent. The head motions of the volunteer studies were also reproduced using a mannequin head on a motorized stage to assess how well the proposed motion measurement system worked when used for motion correction. The results indicated that even though the system improved image quality for all postures, the reclining and supine postures could provide better image quality than the normal sitting posture.


Assuntos
Encéfalo/diagnóstico por imagem , Tomografia por Emissão de Pósitrons/métodos , Postura Sentada , Decúbito Dorsal , Adulto , Feminino , Movimentos da Cabeça , Humanos , Masculino , Imagens de Fantasmas , Rotação , Software , Adulto Jovem
17.
Phys Med Biol ; 64(9): 095014, 2019 04 29.
Artigo em Inglês | MEDLINE | ID: mdl-30978704

RESUMO

Parallax error caused by the detector crystal thickness degrades spatial resolution at the peripheral regions of the field-of-view (FOV) of a scanner. To resolve this issue, depth-of-interaction (DOI) measurement is a promising solution to improve the spatial resolution and its uniformity over the entire FOV. Even though DOI detectors have been used in dedicated systems with a small ring diameter such as for the human brain, breast and small animals, the use of DOI detectors for a large bore whole-body PET system has not been demonstrated yet. We have developed a four-layered DOI detector, and its potential for a brain dedicated system has been proven in our previous development. In the present work, we investigated the use of the four-layer DOI detector for a large bore PET system by developing the world's first whole-body prototype. We evaluated its performance characteristics in accordance with the NEMA NU 2 standard. Furthermore, the impact of incorporating DOI information was evaluated with the NEMA NU 4 image quality phantom. Point source images were reconstructed with a filtered back projection (FBP), and an average spatial resolution of 5.2 ± 0.7 mm was obtained. For the FBP image, the four-layer DOI information improved the radial spatial resolution by 48% at the 20 cm offset position. The peak noise-equivalent count rate (NECR) was 22.9 kcps at 7.4 kBq ml-1 and the scatter fraction was 44%. The system sensitivity was 5.9 kcps MBq-1. For the NEMA NU 2 image quality phantom, the 10 mm sphere was clearly visualized without any artifacts. For the NEMA NU 4 image quality phantom, we measured the phantom at 0, 10 and 20 cm offset positions. As a result, we found the image with four-layer DOI could visualize the 2 mm-diameter hot cylinder although it could not be recognized on the image without DOI. The average improvements in the recovery coefficients for the five hot rods (1-5 mm) were 0.3%, 4.4% and 26.3% at the 0, 10 and 20 cm offset positions, respectively (except for the 1 mm-diameter rod at the 20 cm offset position). Although several practical issues (such as adding end-shields) remain to be addressed before the scanner is ready for clinical use, we showed that the four-layer DOI technology provided higher and more uniform spatial resolution over the FOV and improved contrast for small uptake regions located at the peripheral FOV, which could improve detectability of small and distal lesions such as nodal metastases, especially in obese patients.


Assuntos
Tomografia por Emissão de Pósitrons/instrumentação , Desenho de Equipamento , Humanos , Imagens de Fantasmas , Sensibilidade e Especificidade
18.
Sci Rep ; 9(1): 6537, 2019 04 25.
Artigo em Inglês | MEDLINE | ID: mdl-31024057

RESUMO

This work presents a simulation study evaluating relative biological effectiveness at 10% survival fraction (RBE10) of several different positron-emitting radionuclides in heavy ion treatment systems, and comparing these to the RBE10s of their non-radioactive counterparts. RBE10 is evaluated as a function of depth for three positron-emitting radioactive ion beams (10C, 11C and 15O) and two stable ion beams (12C and 16O) using the modified microdosimetric kinetic model (MKM) in a heterogeneous skull phantom subject to a rectangular 50 mm × 50 mm × 60 mm spread out Bragg peak. We demonstrate that the RBE10 of the positron-emitting radioactive beams is almost identical to the corresponding stable isotopes. The potential improvement in PET quality assurance image quality which is obtained when using radioactive beams is evaluated by comparing the signal to background ratios of positron annihilations at different intra- and post-irradiation time points. Finally, the incidental dose to the patient resulting from the use of radioactive beams is also quantified and shown to be negligible.


Assuntos
Radioterapia com Íons Pesados , Método de Monte Carlo , Radioatividade , Simulação por Computador , Relação Dose-Resposta à Radiação , Elétrons , Humanos , Imagens de Fantasmas , Dosagem Radioterapêutica , Eficiência Biológica Relativa
19.
Phys Med Biol ; 64(6): 065004, 2019 03 08.
Artigo em Inglês | MEDLINE | ID: mdl-30673654

RESUMO

A strong demand is expected for high-sensitivity, high-resolution and low-cost brain positron emission tomography (PET) imaging for early diagnosis of dementia, as well as for general neuroscience studies. Therefore, we have proposed novel geometries of a hemisphere detector arrangement for high-sensitivity brain imaging, in which an add-on detector at the chin position or neck position helps in sensitivity uniformity improvement. In this study, we developed the first prototype system for proof-of-concept using four-layer depth-of-interaction detectors, each of which consisted of 16 × 16 × 4 Zr-doped GSO crystals with dimensions of 2.8 × 2.8 × 7.5 mm3 and a high-sensitivity 64-channel flat-panel photomultiplier tube. We used 47 detectors to form a hemisphere detector with a hemisphere shape of 25 cm inner diameter and 50 cm outer diameter, and we used seven detectors for each of the add-on detectors. The total detector number of 54 was about one-fourth that of a typical whole-body PET scanner. The hemisphere detector for the prototype system was realized by multiple rings having different numbers of detectors and a cross-shaped top detector unit covering the top. Performance evaluation showed uniform spatial resolutions of 3-4 mm by the filtered back-projection method. Imaging tests of a hot-rod phantom done with an iterative method were able to resolve 2.2 mm rods. Peak sensitivity was measured as more than 10% at a region near the top of the head, which was achieved with the help of the top detector unit. In addition, using the prototype system, we performed the first FDG clinical test with a healthy volunteer. The results showed that the proposed geometries had high potential for realizing high-sensitivity, high-resolution, and low-cost brain PET imaging. As for the add-on detector position, it was shown that the neck position resulted in higher sensitivity and wider field of view (FOV) than the chin position because the add-on detector at the neck position can be placed continuously to the hemisphere detector and close to the FOV.


Assuntos
Mapeamento Encefálico/instrumentação , Encéfalo/diagnóstico por imagem , Queixo/diagnóstico por imagem , Dispositivos de Proteção da Cabeça/normas , Cabeça/diagnóstico por imagem , Imagens de Fantasmas , Tomografia por Emissão de Pósitrons/instrumentação , Adulto , Mapeamento Encefálico/métodos , Desenho de Equipamento , Humanos , Processamento de Imagem Assistida por Computador/métodos , Masculino , Neuroimagem/instrumentação , Neuroimagem/métodos , Tomografia por Emissão de Pósitrons/métodos
20.
Biomed Phys Eng Express ; 6(1): 015012, 2019 12 19.
Artigo em Inglês | MEDLINE | ID: mdl-33438600

RESUMO

Brain PET imaging has important roles in neurology, neuro-oncology and molecular imaging research. We have developed a helmet-type PET prototype and have shown that the proposed hemispherical geometry had high potential for realizing high-sensitivity and low-cost brain imaging. However, there is no standard performance evaluation method for helmet-type PET, which would be a bottleneck to its commercialization. Therefore, we investigated appropriate performance evaluation methods for a helmet-type PET based on the NEMA NU 2-2018 standards. For those measurement methods that are not applicable to the helmet-type PET, we changed them while keeping the basic concept of the original NEMA standards. We measured spatial resolution, sensitivity, scatter fraction, count rate characteristics, accuracy of corrections for count losses and randoms, and image quality. We partially changed the measurement methods by making brain-size phantoms and by optimizing the length or the position of radioactive sources. The spatial resolution was 2.8 mm at 1-cm offset position by the filtered back-projection method. Sensitivities measured by the NEMA original setup and the proposed setup were 13.4 and 57.1 kcps/MBq. The respective values measured with our developed brain-size scatter phantom and with the conventional whole-body-size scatter phantom were: scatter fractions of 35% and 35%; peak NECRs of 25.1 kcps at 3.2 kBq/ml and 19.8 kcps at 2.6 kBq/ml ; and maximum absolute biases of 5.5% and 16.0%. The image quality was evaluated with the developed brain-size phantom, and good image quality was obtained. The helmet-type PET prototype showed high-sensitivity even with the small number of 54 detectors. The spatial resolution was better than 4.0 mm over the field-of-view. In conclusion, we proposed the performance evaluation methods for a brain-dedicated PET system with a hemispherical geometry. The proposed method could facilitate evaluation of performance characteristics of brain-dedicated PET scanners and optimization of its scanning and reconstruction parameters.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...